Separation and purification of nitrogen bases



J. R. BAILEY 2,035,583

SEPARATION AND PURIFICATION OF NITROGEN BASES Marek 31, 1936.

Filed Feb. 4, 1952 IY (An yatented 3i, 193

aun 2 st- "f: GEN pas James R. Bailey, Austin, Tex., Oil Company ofCalifornia, i a coration cil California Application February 4, iosa, f(ci. aso-3s) i fr:

gible amounts of basic nitrogenous material. The

results .showed clearly that the crude oil itself does not contain anysubstantial amounts of basic nitrogen compounds.

-I have discovered that the process of ation generates basic organicnitrogen compounds not present in the original crude oil. Thetemperature's at which this conversion occurs are the usual distillationtemperatures for the separation of crude oill into its fractions such asgasoline, kerosene', gas oil, lubricating oil and arey usually below thecracking temperatures used in the conversion of heavier hydrocarbonsinto` lighter hydrocarbons. While these higher crackingtemperatures areeicient for the generation oi basic nitrogen compounds, the lowernoncracking temperatures also produce organic nitrogen bases fromnon-basic compounds in the oil. Undoubtedly the eiilcient agent is heat,and this conversion of non-basic into basic nitrogen compounds may beobtained as well` by merely heating without distillation to thetemperatures usually employed. The above temperatures vary from 275 F.to, and including 740 F. while the cracking temperatures are muchhigher, varying from 800 F. to l200 F. In the process of distillationoilis heated to diil'erent temperatures to recover various fractions.These temperatures `vary depending on the distillation system employed.Representative temperatures are, however, as follows: For the removal ofprimary gasoline, oil is heated to about 275 F. For theA separate thecrude bases into more simple mix-I 55 tures or individual compounds.

Another object is to septe the yb by fractional acid extraction.

Another object is to resolve the crude acid extract byiractionalneutralization by repeated;

participation of the bases by z. f

In separating the bases from their oil content, I have found itdesirable to first remove the hydrocarbon oil and to thus concentrate`the bases. 'I'here are several ways in which this canv be accomplished.Thus, the nitrogen b may be extracted from the oil by repeated washingwith relatively dilute acid, preferably sulphurlc acid. Another methodis to separate the bases from a major portion of the dilutinglhydrocarbon oil by extracting with a solvent in which the nitrogen basesare soluble but in which a large portion of the diluting hydrocarbon oilinsoluble.

Among the solvents which y be used to extract the nitrogen bases, liquidsulphur dioxide is the most important and universally used. (See U. S.patent No. 911,553.)L Other solvents such as iuriural, aniline,nitrobenzene and isobutyl alcohol, accomplish the same purpose and maybe substituted for the liquid sulphur diomde.

The portion oi the oil which is soluble in the solvent, which portionmay be termed the x-l tract, contains the nitrogenous bodies, but -'=.f=contains a considerable` proportion of hydrocarbon oils, such asaromatic and oleiinic bodies which are soluble in these solvents to aconsiderable extent. I have found it desirable to remove as much oi thediluting oils as sible by extracting the bases with a dilute acid. Theresulting solution m then be completely or fraction-l ally precipitatedby an inorganic base such sodium hydroxide or ,nf-l t. onia to produce a'-1.' ture oi bases substantially i'ree oi contaminating hydrocarbonoil.

The so-called Edeleanu process described in the Patent 911,553 isparticularly well adapted to this process. This invention will be betterunderstood by reference to the drawing which shows one exemplication ofthis process in schematic form. The oil containing the organic nitrogenb is introduced from a source, not shown in the drawing, passes throughline i, at a temperature of about F., and is pumped by a pump 2, at apressure of about 25 pounds, through heat exchanger 3 in heat exchangewith the rate r flowing from surge tank via pump i5, line i6,

valve i1, lines 2li and 2l and'valve i8 into heater 22. The ow ofraiilnate may be controlled by proper manipulation of valves Il and i5.In case it is not desired to cool the incoming oil, valve it (which isclosed when railinate is circulating through heat exchanger 3) may beopened and y by closing valves I1 and I8, theramnate from tank I4 may bepassed directly into heater 22.

The oil, leaving exchanger 3, cooled to about 20 F., is forced into thebottom of the SO2 extractor 5 through jets 4 and meets a stream ofliquid sulphur dioxide flowing through line 4| and jets 6. The SO2 inits passage downward through the oil dissolves therefrom the nitrogenousbodies together with the aromatic and oletlnic fractions.

The solution of these bodies in SO2 being heavier than the originalhydrocarbon oil drops to the bottom of the extractor 5. The hydrocarbonoil (raffinate) being lighter than the sulphur dioxide extract rises tothe top where it is removed throughline 1. The rafnate contains some SO2in solution and some extract as entrained particles. The mixtureisdischarged into the raflnate or continuous decanter 8. The SO2 extractwhich has settled in 8 is'removed through line4 I0 and joins the extractwithdrawn through line 9. Lines 9 and I0 join to form line |I whichcarries the extract to the extract tank |2.

The raiilnate freed of extract ows into surge tank I4 from which it iswithdrawn by pump I5 and forced through line I6 either through line 20and/or valve I9 as previously described. The rafilnate then passes intoheater 22 and then into an SO2 evaporator 23, operating at a` pressureof about 75 pounds and a temperature of about 150 F. The dissolved SO2is removed through the top of evaporator 23 through line 24 and forcedby means of compressor 28 into cooler 3| through line 30, and from thiscooler through line 32 and into the SO2 storage tank 33. The ralnateleaving evaporator 23 is pumped through lheater 26 where itis heated toabout 200 F., and introduced into rafllnate evaporator 26 operating at apressure of about one-half pound absolute. The raiiinate freed ofSOz iswithdrawn from evaporator 26 by pump |05 and introduced into the ramnatestorage tank |06. y

The sulphur dioxide gas liberated in evaporator 26 flows through line 21and vacuum pump 29 into the suction side of compressor 28 from where itgoes into storage as previously described.

The extract collected in tank I2 passes by means of pump 42 throughvalve 43 into heat exchanger 31 where it is preheated by warm liquidsulphur dioxide coming from tank 33 via valve 36. The cooled liquidsulphur dioxide coming from heat exchanger 31 through valve 3 5 passesinto' vaporizer 38, where the temperature of the SO2 is lowered toapproximately 20 F. by vaporizing a portion of the SO2 under reducedpressure. The vaporized SO2 passes via valve |04 into line 39 and thenthrough booster compressor ||0 to compressor 28 where it isre-compressed and passed by means of line 30 into cooler 3| where it isliquefied and passed by means of line 32 to sulphur dioxide storage tank33.

The extract collected in tank I2 is pumped by pump 42, valve 44 beingclosed, through heat exchangers 31 and heater 45 into the extractevaporator 46. The temperature of the extract on reaching the evaporator46 is about 100 F., and the pressure is about '15 pounds. 'I'heevaporated S02 is removed through line 41, and compressor |08 V intocooler 48 where it is liqueiled and then through lines 49 and 32 intothe SO2 storage tank 33. The extract partially'ireed of SO2 dischargesfrom the evaporator 46 through lines 5I and 52 into a cooler 5? I Bycontrolling the temperature and pressure in to about atmosphericpressure. However any degree of pressure may be maintained in extractor51 by controlling valve 54. It is preferable to operate at the elevatedpressure to overcome the back pressure of the system. The extract passesthrough jets 56 into the bottom of the lead or ceramic lined extractor51 where it is treated countercurrently with a stream of cold water,introduced through line andA jets 58,. The lighter hydrocarbon oil freedof organic nitrogen bases i flows through line 59 into the separator 60where the oil is removed through line 6| and the aqueous layer throughline 63. The water extract from the SO2 extract contains small amountsof SO2 and all the nitrogen bases in the .form of acid sulfites insolution. This water solution is discharged through line 62 and joinsline 63 also carrying dissolved acid` sultes of the. nitrogen baseswithdrawn from the bottom of 60. Lines 62 and 63 join to form line 64through which the aqueous solution of the bases passes through heater 65into evaporator 66. The water is heated sufficiently to drive oil' anySO2 dissolved therein.

The remaining SO2 is removed through rectifyingv column 61. which isoperated to reflux water and permit substantially dry SO2 to pass.TheSOz gas ows through line 68 into the salt dryer 69 where remainingwater vapor is removed, through line 10, into the suction side ofcompressor 29. The evaporator 66 may be operated at an elevated orsub-atmospheric pressure as desired.

The SO: freed solution of the nitrogen bases ows from evaporator 66,pump through heater 1| into line 12 where it meets a stream of causticsolution introduced from tank 13 by means of pump 14. The solutionpasses through agitator 15 into separator 16 where the nitrogen basesfreed by the addition of caustic, are removed at the top through line 11and subsequently pass through heater 18 into a fractionating column '19.Conventional reilux condenser 84 may be provided and steam may beintroduced at the bottom through jets 80.'

The nitrogen bases entering the fractionatin column 19 are fractionatedinto various cuts which may be removed as side cuts 82, 83 and as abottom fraction through 8|.l The vapors discharge through line |03 intocondenser 85 and separator 86. In separator 96 the nitrogen base vaporsarelcondensed and removed via 81 wlile the water vapor` passesuncondensed through line 86. The water vapors emerging from separator 86through line 88 are introduced into the suction side of aconventionalvacuum steam jet 89 and is introduced into a barometriccondenser 90 where they meet a stream of water at about Gil-'10 F.entering through line |I2. The uncondensed vapors which may includefixed gases pass through line 9| into the suction` side of vacuum pump92 and subsequently are liquefied by owing through cooler 93.

The sodium sulte solution formed by the addition of sodium hydroxide tothe nitrogen bases in solution is discharged from separator 16 throughline S4, into concentrator 95. The solution is heated suiilciently bysteam coil SS to drive onthe major portion of the water which is removedby means of line 91. 7 sulte solution passes through line S8 into the ylead lined treater S9 into which a stream of dilute desired degree ofpressure but it is preferred to operate at as low a pressure as possiblein order to avoid the decomposition or cracking of the nitrogen bases.Pressures as low as 1-25 mm. of mercury absolute pressure may be usedand are obtainable in the above apparatus. The use of a vacuum steam jetand barometric condenser 9@ permits of condensation of steam by ordinarycooling water.

It is well known that liquid sulphur dioxide extracts from petroleumdistillates contain a large number of compounds such as unsaturated,aromatic and sulphur bodies. Experimentsconvducted on kerosene andheavier fractions indicate that the resulting product afterSOzextraction is practically nitrogen free.. These nitrogen bodiesare'found in the SO2 soluble fraction. The exact condition in which thenitrogen bases are present in the liquid SO2 extract is not known. Ibelieve, however, that there is strong evidence that these nitrogenbases are present partly combined with sulphur dioxide as sulphurdioxide addition products and partly as free bases dissolved in theextract.

The extract from the liquid sulphur dioxideV treatment is forced underpressure into a separating chamber where some of the sulphur dioxide isdistilled ofi. The remaining extract containing only small amounts oiSO2 is pumped into a contact chamber where it is washed with water. TheSO2 is converted into HzSOa which reacts with the organic nitrogen basesto form soluble suliites. A subsequent heating of this layer afterseparation from the petroleum fractions may liberate additional SO2which may be dried and recovered. The bases present in the aqueous layermay be liberated by treatment with caustic. The caustic solution issteam distilled and the bases recovered. It should be noted that thisprocessmay operate in a continuous manner and that the amount of basicmaterials required is reduced to a minimum as no acid is added toextract the bases.

This mixture of crude bases may be fractionated as shown and thesefractions or` the crude mixture itself may be further resolved bychemical methods into purer and simpler mixtures and even into purecompounds.

As was stated previously, the bases may be extracted either from thepetroleum oil or from the extract or other concentrate of these basesVby means of dilute acids such as sulphurousl acid,

.- sulphuric, nitric or other inorganic acids or by means of relativelystrong organic acids such as acetic, chloracetic, oxalic acids or acidicsubstances such as picric acid, etc.

The result of the acid or solventextraction is a complex mixture ofaromatic and naphthenic nitrogen compounds, partly of the pyrrole typeand partly of the pyridine and piperidine type. The number of the basesisolated from any fraction in which they occur is undoubtedly very'large. Their nature depends, to a large extent,

The concentrated sodium' upon the source from which they are isolated.They range from low boiling liquids to comparatively high meltingsolids. As a rule, a. mixture' of the aforementioned bases has a ratherpungent odor and tends to darken on standing.

These crude mixtures may be purified and re- Y,

operation advantage istaken-of the diierent basicity oi these bases andtheir relative reactivity with various acids or salts.

A. complex mixture of bases may be separated into several more simpleones, or pure compounds, by the `addition of various reagents capable offorming salts with the nitrogen bases present. Some of `the bases formeasily separable salts with the common inorganic or organic acids.

Various salts. are capable of forming salts or double salts with some oithe bases present in a crude mixture, so that on separation of theprod-v ucts formed a simpler aggregate of bases is obtained or abase isremoved from its impurities in pure form.

For instance, sodium ferrocyanide in dilute hydrochloric acid solutioncombines with some of the bases to form nicely crystallizing, well denedprecipitates. These precipitates may be removed from the mixture leavinga more simple num, palladium, gold, cadmium, iron (ferrous and ferrie),potassium dichromate, etc. Thus, with the 2.3.8 trimethylquinoline base,which .may be isolated from the nitrogen bases present in kerosenedistillate, -gold chloride forms a salt of yellow color resembling thepicrate of said base and recrystallizing from water in long, slenderrods; platinum chloride forms a granular light orange colored salt,difllcultly soluble in Water and alcohol; potassium dichromate gives anorange yellow salt, but crystallized from water in a `fine granulatedcondition; potassium ferrocyanide precipitates the diilicultly solublehydroferrocyanide of a light cream color which in boiling waterdecomposes with the evolution of prussic acid; zinc chloride gives asalt recrystallizing from alcohol in long slender prisms; the mercuriochloride salt' is readily soluble in hot water and hot alcohol andseparates from either solvent in long, slender rods; the stannouschloride salt has solubilities similar to the mercurio chloride )saltand is best crystallized from glacial acetic acid in the formoi rods.

It has been established that some of the bases form insoluble salts withsome vof the salts previously mentioned'while' others do not react atall. By successive'addition of small amounts of these salts, theoriginal mixture is more and more completely broken up into simplerones. Whenthis procedure is carried out on a narrow cut of nitrogenbases obtained by fractional dis- ,be carried out by fractional acidextraction and fractional caustic precipitation. I havefound that thebases in the individual fractions show a considerable difference intheir pH values and that by partial acid extraction followed byfractional caustic precipitation, the distillate fractions or the crude'bases themselves can be separated into much simpler mixtures. I havealso found that through fractional distillation followed by fractionalacid extraction, a large number of bases can be brought to a state ofpurity whereby final recrystallization of the appropriate salts willeffect their complete purification.

In carrying out this fractional extraction, the base is treated withsuccessive amounts of dilute acid such as sulphurlc acid or 'picrlc acidor any of the acids previouslymentioned. The unreacted base is separatedfrom the acid solution of the bases. The unreacted base is againextracted with additional amounts of acid and the extrac- Ation andseparation is repeated until all of the bases are removed by the Iacid.By regulating the strengthof the acid, the bases may be extracted sothat the relatively strong bases are separated from the relatively weakones. Thus, the partition of acid between a number of bases of varyingpH value will be such that the acid will be taken up by the strong basesin a greater degree than by the weakr cries.I The weaker the base, theless the formation of its salt. In this manner, we may resolve the basesinto those of varying degrees of basicity. It will be recognized that byextracting, with increasing or decreasing acid strengths, a furthersegregation according to the above principle into varying strength basesis possible.

The various salt ferent fractions. may be further resolved into freebases by fractional precipitation by alkali. This operation is identicalin principle to acid extraction since it also depends on the relative pHvalue of the bases. It operates oppositely to the acid extraction.Whereas with acid extraction, the stronger bases are preferentiallyremoved, it lis the weaker bases which are preferentially precipitatedby the alkali. By regulating the strength of the alkali, aclassification of the bases may be obtained. Thus, if we made .threeextractions with acidsto obtain three classes of bases in threedifferent salt solutions, then precipltate the bases by treating eachsalt solution with three different treatments with alkali, we will havethen resolved the original mixture of bases into nine fractions ofvarying basicity and purity.

The fractional extraction with acids and bases tends to resolve thebases'into varying basic strengths, also acts to separate the b'ases ofpyridine type from the naphthenic bases, i. e. those of piperldine type.The pyridine bases being strong, will be preferentially dissolved by theacid and the piperidines will be preferentially liberated from themixture of salts of these bases.

solutions, each containing dif.

'I'he above methods may be employed ,for the separation of purecomponents from the crude mixture of4 bases.

-A kerosene boiling between 35o-,550 F., obtained from a CaliforniaMcKittrick asphaltic crude, was extracted with liquid SO2. The SO:extract was freed of SO: and washed with dilute sulphuric acid. The acidsolutions were neutralized with sodium hydroxide and the freed base wasseparatedfrom the sodium sulphate solu tion. The crude bases werefractionally distilled, and distillates re-distilled to produce narrowcuts. The distillation was carried out under very high vacuum tominimize decomposition.l The fraction boiling at atmospheric pressure at276- 277 C. was isolated. This fraction contains approximately 18% of apure base which is 2,3,8, trimethylquinoline. A very. satisfactorymethod for isolation of this base from the other bases in this fractionis to separate it in the form of the picrate admixed with the picrate ofthe base 'Cisl-MN, another base present in this fraction,

by the addition of successive portions of 20 grams of picrlc acid in 50c. c. of 50% acetic acid to 100 c. c. of the above distillation fractiondissolved in 350 c. c. of 50% acetic acid. The picrate of the latterbase in contrast with that of the former is' readily soluble in bothbenzene and alcohol and, therefore, a mixture of these salts is easilyseparated.

A second method of isolation of 2,3,8, tri methylquinoline is offeredthrough its acid sul--` phate. APreliminary tests are made to indicatethe amount of 50% sulphuric acid to be used as -well as theconcentration of this base in diil'erent fractions. Through the sulphatetest fractions boiling from 274 to 280 C. (748 m. m.) inclusive, werefound to contain 2,3,8, trimethylquinonllne with the maximum amount ofaround 20% in the 276 to 277 C. fraction. Since the sulphate of the baseCmHzsN is very soluble, it is not precipitated but can be subsequentlyseparated as picrate. However, admixed with this sulphate there occursin small amount the sulphate of a second base having the formula CnHiaN.This latter base is an odorless solid melting at 43 and boiling at 278.9C. (748 m. m.) It reacts with formaldehyde and with methyl iodide formsthe cor- -CHx CH: N

Characteristic of this substance is its faint fecal odor. It is readilysoluble in the common organic solvents, very diilcultly soluble in watereven at aosaoas tions of the kerosene bases. Dissolved in hot gla j cialacetic acid,it separates on cooling in arborescent canary'yeilowcrystals which blacken and decompose with. gas evolution. at 242=245 C.0n heating in ammonium hydroxide solution the base is liberated.

The resolution of the bases into mixtures of varying degrees of basicstrength is especially useful in the preparation of strong organic baseswhich are oil soluble. All of these bases are, of course, oil soluble.The stronger bases are useful as emulsiers for oil. Thus, the fatty acidsalts of these bases may be useful to form oil soluble soaps which maybe used in making emulsiable oil. Obviously, the stronger the base, themore emoient it will be for this purpose and the separation of theweaker bases from the stronger bases results in a purer, stronger andmore emcient oil soluble base. y

In like manner, the removal of the hydroaromatic bases from the aromaticbase, i. e. the piperidine type bases from the pyridine type baseresuits in a purer compound to be used as onintermediate in thepreparation of phthalone dyes of the methyl quinoline type.

The 2,3,S trimethylquinoiine condenses on fusion with phthalic anhydrideto form a phthalone dye intermediate which when sulphonated, forms abeautiful yellow dye. The reaction may be carried out by simply fusingthe intermediate at a temperature of 200 C. for a period of four hours.The resulting dye is extremely stable.

In like manner, the crude mixture of pyridine type bases obtainedpreferably by fractional extraction-to separate it from thehydroaromatic bases may be used instead of the pure 2,33,trimethyiquinoiine. The crude mixture of these bases contain a largenumber of quinolines which have the methyl group in proper position forcondensation with phthalic anhydride. For example, 2L3 dimethylquinolineand 2,4 dimethylquinollne are present in the crude mixture. Thequinolines methylated at the 2 position are capable of condensation withphthalic anhydride. Where such a condensation reaction is carried outwith phthalic anhydride, the quinolines metbylated in the abovementioned positions` react. Thus, where we have a mixture containingother quinolines besides the ones methylated in the proper position,others not so constituted, addition of phthalic anhydride will cause aselective condensation, i. e. only the quinolines methylated in theproper positions react. By fractional acid extraction and causticprecipitation, a particular cut may be narrowed down to a point wherethe particular methylated quinolines predominate. Addition of phthalicanhydride will cause the formation of phthalone dyes. Thus by fractionalacid extraction and caustic precipitation, a complex mixture of basesmay be narrowed down to a point where phthalone dye formation ismaterially facilitated. The same results may of course, be obtained byfractional precipitation of the various bases as salts.

The various examples set forth herein are not to be considered aslimitations upon .my invention. As to the scope thereof, reference ismade to the appended claims.

I claim:

1. A method of separating organic nitrogen bases from petroleumfractions which comprises extracting said fractions with liquid sulphurdioxide to form an extract containing said organic nitrogen bases,hydrocarbon oil and liquid suls phur diomde. removing a portion of thesulphur .x s dioxide from said` extract and contacting the extract withwater, septing an containing nitrogen bases from an and liberating thenitrogen bases from said aqueous phase by addition thereto of aninorganic hydroxide. i 2. A method of uw ting organic nitrogen basesfrom petroleum fractions which comps extracting said fractions withliguid sulphur dloxide to forni an extract containing said organicnitrogen bases, hydrccarbonoil andvliquid sulphur dioxide, removing aportion of the sulphur dioxide from said extract and contacting theremaining extract with water, separating an aqueous phase containingnitrogen bases from au oil phase, liberating the nitrogen bases fromsaid aqueous phase by addition thereto of a solution of'an alkali metalhydroxide and separating the liberated nitrogen :c

3. A method of' separating organic nitrogen bases from petroleumfractions which comprises extracting said fractions with liquid sulphurdioxide to form an extract containing said organic nitrogen bases,hydrocarbonv oil and liquid sulphur dioxide, removing a portion' of thesulphur dioxide from said extract4 and contacting the remaining extractwith water, separating an aqueousphase containing nitrogen bases from anoil phase, liberating the nitrogen bases from said Y aqueous phase bycontacting said aqueous phase with an alkali metal hydroxide, separatingthe liberated nitrogen bases and fractionally distilling the liberatedbasesat pressures lessthan atmospheric.

d. A method of separating nitrogen bases from kerosene produced fromasphalt base crude oil, which comprises extracting said kerosene withliquid sulphur dioxide, separating the sulphur dioxide extrnct from theportion of the kerosene insoluble in liquid sulphur dioxide, separatingthe sulphur dioxide from the extract to produce a crude mixture ofbases, distilling said crude mixture to obtain a fraction containingcomponents having a boiling range of 276-277 C. and adding picric acidto said fraction to precipitate the vpicrate of 2.3.3trimethylquinoline, separating the piorate from. the remainder of thefraction and liberating the 2.3.8 trimethylquinoline from the picrate byreaction with an hydroxide.V

5. d method of separating nitrogen bases from kerosene produced fromasphalt base crude oil which comprises extracting said kkerosene withliquid sulphur dioxide, separating a sulphur diox- -ide extract from theportion of the kerosene in? soluble in liquid sulphur dioxide, removingthe sulphur dioxide from the extractfto produce a crude mixture ofnitrogen bases, extracting said crude mixture with an inorganic acid toform an aqueous solution of salts of the nitrogen bases, liberating thebas from said aqueous solution by means of an inorganic hydroxide,separating the nitrogen bases, fractionally distilling said separatedbases to obtain a fraction containing components having a boiling pointrange of approxinitrogen bases, hydrocarbon oil and liquid sulphurdioxide, removing a portion of the sulphur dioxide from the saidextract, contacting the remaining mixture with water and separating anaqueous solution containing acid sulphites of the nitrogen bases.

7. A method of separating organic nitrogen bases from petroleumfractions which comprises extracting said fractions with liquid sulphurdioxide to form an extract containing saidorganic nitrogen bases,lhydrocarbon oil and Aliquid sulphur dioxide, removing a portion of thesulphur dioxide from the saidextract, contacting the remaining mixturewith water, separating an aqueous solution containing acid sulphites ofthe nitrogen bases and separating the nitrogen bases from said aqueoussolution.

JAMES R. BAILEY.

